Disk brake and brake pad set for a disk brake

ABSTRACT

In the case of a disk brake with two brake pads ( 4, 6 ) arranged opposite each other on either side of s brake disk ( 2 ) where the brake pads ( 4, 6 ) is capable of being pressed against the brake disk ( 2 ) for braking purposes, wherein the brake pads ( 4, 6 ) comprise a carrier plate ( 8 ) and a friction lining layer ( 10, 12 ) arranged thereupon and wherein the friction lining layers ( 10, 12 ) comprise areas ( 14, 16, 18, 20 ) of reduced thickness, it is provided for the brake pads ( 4, 6 ) located on either side of the brake disk ( 2 ) not being arranged mirror-symmetrically in relation to the areas ( 14, 16, 18, 20 ) of reduced layer thickness of the friction lining layers ( 10, 12 ) arranged opposite each other.

[0001] The invention relates to a disk brake and a brake pad set for adisk brake according to the precharacterizing part of claims 1 and 2.

[0002] Such disk brakes are required in the vehicle sector. It is commonpractice to configure the friction linings fastened to the carrierplates of the brake pads with bevelled faces, i.e. not with surfacesextending parallel to the brake disk or the carrier plate.

[0003] The brake pads fixed on either side of the disk brake havefriction linings with bevelled surfaces of mirror-inverted arrangement.

[0004] Disk brakes are complex, oscillatory systems which are excited tooscillate by the friction forces acting in the contact surfaces betweenthe friction linings and the brake disk.

[0005] On of these oscillation problems is the so-called creaking ofbrakes. This phenomenon is due to low-frequency oscillations in thefrequency range from approximately 20 to 150 Hz occurring during thetransition from adherence to friction and at an extremely low velocityof the vehicle. Creaking of the brakes occurs in particular in high-dutyvehicles with automatic gearbox due to the driving torque beingpermanently applied to the drive shaft.

[0006] In the past few years oscillation problems have to a growingextent been encountered in the automotive sector. One reason for this isthe consequent realization of light-weight construction and costreduction concepts. On the other hand, the vehicle buyers makeincreasing demands on the comfort to be offered by a vehicle and requirethe disturbing driving noises to be eliminated.

[0007] The so-called slip stick effect is blamed for the occurrence ofthe creaking noises. The slip stick effect is the alternate adherenceand sliding of the friction linings to/on the brake disk.

[0008] In the vehicle creaking occurs in two different situations. Atypical case, which frequently occurs in high-duty vehicles withautomatic gearbox, is release of the vehicle brake with a driving torquebeing applied. If a driving torque acts upon the drive shaft while avehicle stands still with the brake being applied, slow release of thebrake may cause a clearly audible crack or even a penetrating buzzingnoise. The driving torque needs not necessarily be generated by theengine, it may also be produced by a gravitational force occurring whenthe vehicle is in downhill position. In this case, too, the brake creaksif it is slowly released and a certain critical contact pressure of thebrake lining has been reached. The buzzing noise described may occurduring uniform and slow movement of the vehicle and constant contactpressure for an extended period of time.

[0009] Even when the vehicle is braked at higher velocities a shortcreaking noise may be audible during the transition from friction toadherence immediately before the vehicle stops.

[0010] It is the object of the invention to provide a disk brake or abrake pad set for a disk brake by means of which occurrence oflow-frequency noises is to be prevented.

[0011] According to the invention this object is to be solved incompliance with the features stated in claim 1 or 2.

[0012] The invention provides in a preferable manner for the frictionlinings of the brake pads to comprise areas of reduced layer thicknesswhich are not of mirror-inverted arrangement in the brake pads inrelation to the brake disk. Since the friction linings relative to aplane in the brake disk are not arranged mirror-symmetrically, eitherside of the brake disk presents different frictional forces therebyinducing different oscillations on either side of the brake disk, whichaffects the self-excitation of the oscillation and thus the suppressesoccurrence of low-frequency oscillations in the frequency range from 150Hz, and in particular resonance phenomena.

[0013] The bevelled friction linings are configured so that the areas ofreduced layer thickness have a surface inclined towards the carrierplates and incline, e.g. at an angle of approximately 10 to 45° to thecarrier plate, tangentially to the outside in the direction of thecarrier plate.

[0014] The separating line between the areas of the friction lininglayer with identical layer thickness and the areas of reduced layerthickness may extend in parallel to the symmetrically bisecting line ofthe brake disk, which extends in radial direction of the brake disk, orat an angle to said symmetrically bisecting line. The angle to saidsymmetrically bisecting line may be in the range from ±0 to 60°,preferably in the range between ±10 and 30°.

[0015] For example, in the case of brake pad pairs located opposite eachother it is envisaged that said separating line extends in oppositedirection on both sides of the brake disk and thus notmirror-symmetrically.

[0016] Further preferred embodiments are described in the subclaims.

[0017] Hereunder embodiments of the invention are explained in detailwith reference to the drawings in which:

[0018]FIG. 1 illustrates a first embodiment of a brake pad set for adisk brake with the brake pads being, for clarity's sake, unfolded by90° to the outside into the drawing plane,

[0019]FIG. 2 illustrates a piston-side brake pad,

[0020]FIG. 3 illustrates the brake pad complementary to the brake pad ofFIG. 2,

[0021]FIGS. 4 and 5 illustrate further embodiments of the invention.

[0022] In FIG. 1 the brake disk 2 rotating during driving operation isarranged between the brake pads 4, 6. To illustrate the friction liningsurface the brake pads 4, 6 are folded to the outside by 90° out of itsnormally parallel position to the brake disk 2.

[0023] The friction lining of each brake pad 4, 6 comprises a centralarea 22 of constant layer thickness or a layer thickness slightlyreducing towards the outlet end of the brake pad. Such a slightlyinclined friction lining surface in the central area 22, which is notshown in the drawings, prevents squealing caused by friction by shiftingof the center of pressure. The friction lining layers 10, 12 comprise atthe ends of the brake pads 4, 6 areas of reduced layer thickness 14, 16,18, 20 which are not arranged mirror-symmetrically in the brake pads 4,6 in relation to a mirror plane extending longitudinally to the brakedisk 2. This prevents the self-excitation of braking oscillations, inparticular oscillations in the frequency range from approximately 20 to150 Hz. The bevelled faces of friction linings located opposite eachother are thus arranged in different ways thus preventing regularscoring on the brake disk 2, which would occur in the case ofmirror-inverted arrangement of the friction lining. The slip stickeffects known as creaking of brakes with simultaneous tilting of thefriction linings at low velocities of the vehicle are reliablyprevented.

[0024]FIGS. 2 and 3 illustrate a brake pad pair with FIG. 2 showing thepiston-side brake pad and FIG. 3 the brake pad on the opposite side. Inthe embodiment the bevel of the area of reduced layer thickness extendsat an angle of 20° to the friction lining surface in the central area 22or to the carrier plate 8. Said bevel of the areas 14, 16, 18, 20 mayextend at an angle ranging between approximately 10 and 45°. Theseparating line between the central area 22 of the friction lininglayers 10, 12 and the area of reduced layer thickness extends at anangle of approximately ±22° to the dial symmetrically bisecting line 28of the brake pads 4, 6. The separating line may also extend at an angleranging between ±0 and 60°, preferably ±10 and 30°.

[0025]FIG. 4 illustrates an alternative embodiment of a brake pad on theopposite side, a section along a section line extending orthogonally tothe symmetrically bisecting line 28, and FIG. 5 shows a schematicrepresentation of the brake pad pair of FIG. 4 in a representationsimilar to that of FIG. 1.

1. Disk brake comprising two brake pads (4, 6) arranged opposite eachother on either side of a brake disk (2) and being capable of beingpressed against the brake disk (2) for braking purposes, with thebraking pads (4, 6) comprising a carrier plate (8) and a friction lininglayer (10, 12) arranged thereupon, and the friction lining layers (10,12) comprising a central area (22) of identical layer thickness and anarea (14, 16, 18, 20) of reduced layer thickness at at least one end ofthe brake pads (4, 6) in tangential direction of the brake disk (2),with the brake pads (4, 6) positioned on either side of the brake disk(2) not being arranged mirror-symmetrically in relation to the areas(14, 16, 18, 20) of reduced layer thickness of the friction lininglayers (10, 12) arranged opposite each other relatively to the brakedisk (2), wherein, with the purpose of preventing low-frequencyoscillations up to 150 Hz, the separating line (24) between the centralarea (22) and the at least one area (14, 16, 18, 20) of reduced layerthickness extends at an angle of ±10 to 60°, preferably ±10 to 30°, tothe bisecting line (28) of the brake pads (4, 6) extending in radialdirection of the brake disk (2), and that the separating line (24) ofthe brake pads (4, 6) located opposite each other are oriented inopposite directions.
 2. Brake pad set for a disk brake comprising twobrake pads (4, 6) located opposite each other on either side of a brakedisk (2), the brake pads being capable of being pressed against thebrake disk (2) for braking purposes, with the brake pads (4, 6)comprising a carrier plate (8) and a friction lining layer (10, 12)arranged thereupon, and the friction lining layers (10, 12) comprising acentral area (22) of identical thickness and at at least one end of thebrake pads (4, 6) in tangential direction of the brake disk (2) an area(14, 16, 18, 20) of reduced thickness, with the brake pads (4, 6)arranged on either side of the brake disk (2) not being arrangedmirror-symmetrically in relation to the areas (14, 16, 18, 20) ofreduced layer thickness of the friction lining layers (10, 12) locatedopposite each other relatively to the brake disk (2), wherein, with thepurpose of preventing low-frequency oscillations up to 150 Hz, theseparating line (24) between the central area (22) and the at least onearea (14, 16, 18, 20) of reduced layer thickness extends at an angle of±10 to 60°, preferably ±10 to 30°, to the bisecting line (28) of thebrake pads (4, 6) extending in radial direction of the brake disk (2),and that the separating line (24) of the brake pads (4, 6) locatedopposite each other are oriented in opposite directions.
 3. Deviceaccording to claim 1 or 2, wherein the surfaces of the areas (14, 16,18, 20) of reduced layer thickness extend to the outside tangentiallytowards the carrier plate (8) in downward direction at an angle ofapproximately 10 to 45°.
 4. Device according to one of claims 1 to 3,wherein each brake pad (4, 6) comprises a plurality of areas (14, 16,18, 20) of reduced layer thickness which are arranged symmetrically oneither side of the symmetrically bisecting line (28) of the respectivebrake pad (4, 6) extending in radial direction of the brake disk (2). 5.Device according to one of claims 1 to 3, wherein the areas (14, 16, 18,20) of reduced layer thickness are arranged in tangential direction ofthe brake disk (2) at at least one end of the brake pads (4, 6). 6.Device according to one of claims 1 to 5, wherein the areas (14, 16, 18,20) of reduced layer thickness are arranged at the outlet end (30, 32)of the brake pads (4, 6) relatively to the direction of rotation of thebrake disk (2).